<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Title</title>
</head>
<body>
  <canvas id="canvas" width="400" height="400">
    此浏览器不支持canvas
  </canvas>
</body>
</html>

<script>

  const ctx = document.getElementById('canvas')

  const c = ctx.getContext('2d')

  c.fillStyle = 'red'
  c.fillRect(10,10,100,100)

</script>
